The objectives of the proposed project are: 1: To maintain and to develop the LOU rat system in order to help the research on the IgE physiology. 2: To work in collaboation, on different fields of the IgE physiology 1) with Dr. Henry Metzger on attachment of IgE on rat mast cells, 2) with Dr. Ellen Jarrett on the phenomena of potentiation of the reaginic response by helminth infection, 3) with Dr. Andre Capron on immunity to parasite. 3: To study the role of the Immunoglobulins in the immunity mediated by the macrophages and directed against allografts or tumoral cells, and most especially the role of the IgE antibodies.